Gus Potter

Off on the wrong track! Thanks Daiking.

From the SE side it would be wise to look at how the SIPS panels are held down and get this nutted out. A lot of folk have a gut feel that the wind won't lift the house up and this does not happen..often.. However, the big elephant in the room is that lot's of new houses have big wide doors and openings. Here you have less walls.. they are more like columns so they want to over turn as the wind blows on the side of the house. To stop this effect you often need to rely on the holding down straps to stop each panel overturning. To stop over turning you need "ballast".. something heavy to anchor to and you also need to find a fixing method. The super structure providers often say.. holding down system is for the SE, SE says it's for the super structure (kit) designer. No one wants to take responsibilty (someone should do for competant design.. it's in the statutory CDM regulations) for the fixings / straps etc as this requires design time and coodination.. that comes at a cost which is not spelled out to self builders and the like. I would ask some of the SIPS suppliers for options on how the panels are restrained against overturning. Check the SE design to see what uplifts are occuring at the panels and so on as this will impact on how you are developing up your design. All the best.

Hello Syne. Your nautical approach will appeal to some of the members on BH. It's a good analogy and good questions. I simplify, but if you think about the ground as layers of a cake. Each layer (if clay say, not rock ) moves - expands and contracts by different amounts depending on the moisture content. Each layer of soil also compresses by different amounts depending on how much load you put on it. You can be technical here and try and account for the different layers of soil and found the ICF at a different depth. You could maybe analyse this using an advanced soil model.. academic research.. But in reality the layers of soil are not generally level as this is nature. Any model would be just that. By different depths I mean say plus 300 mm (not a few mm) as this is the point where you could start to excavate too much near the existing founds? A way of simplying this is to found things at roughly the same depth. A clay soil as it shinks and swells will easily lift a house up and down. Syne .. yes your right about the ground. If the clay (say) swells and the house stayed at the same level then this would mean that the founds are sinking into the soil? If you are on rock or chalk then it's different, I have assumed clay here. Now, if you found the ICF raft at the same level as the old house each will move roughly up and down at the same rate at this level (datum). What you are doing here is making educated assumptions. This is the first part. Next (second part) is to look at the ICF material. Often you see a spec for IFC as being able to carry say 150 kPa at 10% compression. That's about 15 tonnes per sq metre. Sounds like plenty, but the insulation is elastic. If you have a thickness of ICF of say 300 mm then to carry this amount of load then the ICF would need to compress by 10% of 300mm = 30 mm..that causes an issues for say a floor slab, the windows and doors won't open, you'll get cracking that will overstress the other parts of the structure. One reason being is that some parts of the ICF will be more heavily loaded than others and move differentially. What we do here is to manage the loads on the ICF down to about say 40 Kpa as a starting point. Now the 30mm compression at 150 kPa is (40/ 150) * 0.1 * 300 = 8.0mm.. this is more on the ball park.. a timber kit can shrink this amount easily for example. The 8.0mm is very rough as there are other factors that are too lengthy to explore for now. Put the two parts back together. If you load up the floors on the old house, say get a heavy fall of snow, the walls are solid, go all the way to the founds, thus the old house does not move (compress) down that much over the eaves to foundation level. It's a solid old house. The extension walls subject to the same load won't compress that much but the IFC will compress.. by say the 8.0mm under full loading. In summary with a bit of good detailing you can account for the ICF movement between the old and the new which is doable, but founding at different depths (bottom of ICF ~ = to bottom of old found depth) can introduce other issues. A good way of looking at this is to say.. well the old house shows no signs of distress, let's not found something at a different depth, more, let's found something at the same depth, try and avoid heavy point loads on the soil, especially near the old founds and see if we can develop a design along these lines that will account for the different behavoir of the ICF insulation and the old walls of the house. Hope this helps.

Hi Keiko909 From memory and a bit of background. I said five years ago but it's probably a bit more than that, but less than ten. I was designing a lot of cold formed steel portal sheds over the UK for the companies that sell these sheds on the mass market. A couple of them had a sideline business where they were buying containers and turning them into business units, one had got a lot of them and turned into a kind of eco B & B hotel. We stacked them up to I think three storeys.. can be done SE wise but it was a lot of work and I'm not sure they made any real money out of it. In terms of the technical spec you have a metal box. Metal is waterproof so this is your vapour barrier. One way of doing it is to put the insulation on the outside so the steel box is on the warm side. If you spend time on BH and ask questions you'll get a lot of help from the folk here that really know their stuff. One thing I learnt when I was doing this is that the container market is even worse than the second and car market. But when I was involved it turned out that there are a lot of brand new containers that come from China that have a one way trip thus not been in slaty air for too long. They never go back.. but the steel is a bit "crap". However you also find that some of them are lined out in high value timber, sometimes protected species not good.. what do you do? Another thing I learnt was that at the time it was cheeper to put stuff in a container and cart from China than to the UK than from Dover to Glasgow! I don't think this economic has changed much? I've seen this done but maybe starting point is what you need to pay for the box and what is left inside it? Hope this helps.

Yes, not easy to source and anything reclaimed at that length and virgin timber requires a bit more thought, may be a bit more bashed about than you want. I would consider the over cladding once you have got all the dusty and wet trades out the way. You may have an oak stair which will have a more "Engineered" look? In the UK we tend to initially think about "solid timber" beams, stairs and so on. In the US and Canada they often rough stuff out then over clad in a higher quality timber. Over cladding can often simplify the structural issues so you get to spend more on the things you see?

Interesting stuff. About five years ago I worked on designs for container conversion with a couple of companies that were doing this in the South of England. You can probably find some of their stuff on the net. All the best. It can be done no doubt so look forward to your posts.

Float the idea to the builder that you may engage the same QS to maintain a watching brief on the "design and build" contract they offer you. I have seen this many times before and the contract offered is often not fair, equitable and reasonable unless they are at least sticking to a recognised standard contract adopted by the industry. Make no mistake a good experienced QS or other professional is worth their weight in gold. A few well chosen words of advice can save you later... They may (QS) even give this advice for free. I do if able!

Well done to you Andy. For all there is a lot to what Andy is doing. ICF etc, sounds like there is a big opening in the front. Although it's done under PD what Andy is doing can add a lot of value to the property.. if it is done right. Imagine it's just an extension not connected to the house. It's also a great way of cutting your teeth which can give you confidence to tackle larger projects if you fancy it. Andy.. sounds like you know what you want so maybe no real need for an "Architect" per say. Many of these "garden buildings" now have a big open front on the high side with bifolds or sliding doors. What you now have is something akin to an open sided, often mono pitched farm shed with a set of doors on the high front elevation. What is required here is to make sure that when the wind blows the building does not fall to the side in the plane of the doors. Here what you often do is to make the side walls, roof and the back wall are stiff. You can try this at home with a cardboard box. Cut out one long side, tape it up along the seams, down to a table and push it along the plane of the doors. You'll see it wants to rotate so if you brace the "gable" it works. For the technically minded this often called a complimentary shear effect. To square this circle the SE will work out the wind load and put bracing or use the panel stiffness on the gables, back wall and roof to show that it works. You'll need to make sure the building is fixed down to something heavy as it also wants to lift up in places. Andy if you can get all the data on the panels, slab and put this into a document. The more info you give the SE the less they need to guess and so on. Also, get the details on how the panels are connected together. No point in having the panel data without the info on how they can interact and connect together. It's a big learning curve to become competant to prove this calculation wise but there are SE's that will do small jobs for enthusiastic beginners so don't loose heart when searching them out. If you do the donkey work on gathering the info then you may get a cracking reasonable price from an SE. One last thing I have observed is that sliding doors need some kind of space above so the roof / lintel over can deflect down. This is a traditional deflection head detail. But I was talking to some fitters of bifold doors the other day and they want to pack the head of the doors tight to stop the mechnism at the top coming loose?

Have you had a look at the other islands? Skye has the bridge but it's quite a busy place now. The North 500 route was an almost too good as a marketing excercise as so many folk are doing it. I have family on Tiree. It's quite an affluent Island but there are others where the land is cheeper. Of course you can't just nip up as the Ferries are often off in the winter and so on but for some that is an attraction.

Hello Eckybloke. You may not be able to do this and it may not suit you if you have young kids. Looks like your ground water flow is towards your garden. What about a small pond on your side of the fence. Make it two different depths, 1.2 - 1.5 m in one spot, 0.3m shelving to zero at the other. This leaves a bit unfrozen at depth but allows frogs and small birds to enter and bathe in the shallow water. Ask you neighbour if you can chuck the soil over the fence to create a planting bund and put some good looking but low growing trees on top of the bund to give you colour all year round, some shelter for the birds at high level and hedgehogs etc at the base. Often you'll find the pond stays partly filled all year round, great for the wildlife, you could even plant some sloe bushes on the bund and make gin. If you have a friendly neighbour then they may well be fine with this type of proposal. Sometimes it's about working with the ground water rather than trying to fight it. It will take less than a day to make the hole with a jcb which can hopefully reach over the fence too. Then you can play for months setting up the pond planting and watching the wildlife discover your garden. It may become stagnent if you over feed it but you can aerate it with small air pump.

Well done you for developing this up.. design is a journey! Often you draw something (professionals often) and realise it can be improved once you have slept on it. One thing to take account of is that you need to tie the timber frame down. When you don't have a heavy outer skin of masonry to provide ballast this gets a little more tricky. Some say.. there is no way that the wind suction on the roof will lift the building off the founds.. and yes you don't see too many failures like this... but if you live in a windy spot with certain pitches of roof then you can get uplift when you don't have a masonry outer skin. Often if you have an extension with big doors on the front and small panels each side (no goal post) which may want to tip over, like a column, they need to be anchored to something heavy. Sean.. If you can post some of your elevation drawings then you may get some more pointers, I'll give you some if I can. Have a look for tie down (holding down) strap details etc on BH. You can embed tie down straps into the founds but they can get in the way, folk can trip over them. It''s also hard to get them to line up with the stud positions, but here you can introduce dummy studs unless you are using SIPS... this means that you don't need to be so accurate when pouring the concrete. You can also fix the holding down straps to the top of the founds and there is a way of doing this in your case which will work as you have plenty edge distance for the fixings (strap to concrete found) and so on. Draw in your tie down straps on the inside of the frame (5.0mm thick) with a bent leg facing in fixed to the founds if you can, to see how that might work. Put a big washer ( 50 x 50x 6.0mm thick) that extends to the inside of the bend of the strap. Depending on what tensile loads you have in the strap you may be ok.. if not you may need a bespoke strap... not a massive cost issue. Much will depend on what tension you have in the strap, hence my point about the elevation drawings. You can also try and use the slab to provide the ballast.. but as you have only light anticrack (A142) reinforcement in the slab it becomes an issue in terms of technical design and justification. Happy researching. Well done again for sticking with it.

"The idea of creating a kick with errant knobbly slates is an excellent tip, something I would have thought about having finished the job." Sorry, lack of clarity on my part. You cut the knobbly bit off (forming a half slate) as often the slate above will not sit right. As you go up the verge you'll have a half slate, full slate width etc. You can create the tilt you want by the detailing the verge flashing.

If you have a good quality slate 3 piles are the most practical (Scotch slate are a bit harder to work with). Do it by eye and how the weight feels in your hand. Try a couple of hundred, stand back and have a look. You'll soon get the hang of it. The density of the slate varies as it's a natural material. Also, some edges will be thicker than others. Once you get them up on the roof and start laying then if the odd one is kicking up just lay it to the side. Some will have say a thin edge, knobbly bit, so you can just trim these when you are up there say for a valley or at the verge where you may put a small tail or kick up to shed the water back into the roof. If you have a lot of slates to do then you can rig up a hap - shelter. You may need to hole them so a holing machine is a great tool to have. I like the ones where you turn the handle like a drill rather than the ones that "punch". In winter a flask of tea or coffee, a radio and a bit of old insulation to keep your feet warm when standing at the holing machine.

Thanks for the heads up Devil. Will aim to be a bit more OT and concise when posting. I you are a self builder you may be placing some reliance on the fact that a BC company is carrying out site "checks". The CDM regulations relate in part to safety during construction and also after completion. If the site checks are no longer taking place then the BC company should advise on what action, if any, is required. Triassic. This could be the reason for asking for a progress report. It may be that they want to limit the site visits to those that are safety critical and rely on photographs for the items that are less risky.

No, this should not happen. Having dealt with the system down south and private BC, experienced some real safety howlers etc. It seems like a race to the bottom. They did away with the clerk of works role years ago. It's only a matter of time before there is a serious accident and folk get killed. The thing is folks (Triassic excluded as asking the question) that these checks, controls and balances are for your safety! Undermine them to save a few quid.. why? Just to concentrate your minds a bit on BH. The CDM statutory regulations include self builders, look them up, you don't have to do too much but if someone gets hurt or worse you could find yourself in the firing line. Yes, it's not a hot topic on BH.. but the consequences can be a lot worse than a bit of condensation or worrying about a bit of cold bridging! Thank you Triassic for you post. Rant over for now!

Just a thought. I wonder what the structural issues are. I would start here. Often with an extension you need to get the pitch so you can get the tiles to work at low angle and if two storey get the flashings / cavity trays to function. One way of making a roof thinner is to close up the spacing of the rafters, however you have more wood that is more conductive than say PIR insulation, law of return and so on. I did a dormer attic conversion where I used cold formed steel rafters and stuck a warm roof on top, managed to squeeeezzzzze it in by about 10mm so it did not stick above the main ridgeline of the house. There are standard sizes available and brackets too so it may be worth a look if you are tight for space. A cold formed steel rafter is just like what you see on a B & Q roof but can carry more load than a timber rafter of similar depth I'll leave out the width for now. You can stick a rubber say EPDM membrane on a shallow pitched roof.

You may be as the cost of maintaining the structural intergity, robustness and tying it all in may far exceed the cost of just adding in a bit of insulation else where. Ledgers can be fine but best to have some compression in the masonry as you need the weight above to top the masonry from rotating etc.. Hangers are not so good at taking horizontal loads, especially if they are retrofitted. When you take away a wall you need to remember that even if it does not appear to be holding something up it may be providing lateral stability to another wall that is, and that wall may be subject to horizontal wind load. That is your starting point.

This requires a bit of lateral thinking. If you are a builder and you get the structural slab too high then you are in trouble. All other things being equal then it's a bit of risk management. Or they may have cast the structural slab too thin hence the 90mm... to fudge it up..

Good points from George showing how you can make a small change that could have a big impact on the cost and buildability. George also mentions the debate about how a steel frame interacts with an existing (assume masonry walls for simplicity) structure. I'll have a stab at this.. to all, please feel free to comment. If you go back a bit, before the days of reasonably priced bifolds etc you often added a modest set of French Doors that maybe were a bit wider than say an existing window. Here, you still had plenty masonry each side to keep the building stable horizontally when the wind blew. Often you could just put in a concrete lintel or a modest steel beam just to hold up say; the wall on a second storey, floor, roof above.. you only had to deal with the vertical loads. But now we are putting in much larger openings and are left with much less brickwork to stop the building from moving from side to side. When you do this you can end up with masonry each side of a large opening that looks more like a column than a wall. One problem that starts to crop up is that a column is much easier to overturn (push over) than a longer length of wall. Also, you have a shorter length of mortar bed to resist the sideways (shear) forces and a few other bits and pieces. @George "I have tended to use the existing building where possible..." The key bit in Georges good comment for me is "..where possible." If the remaining walls won't do the job then often the SE is faced with a dilemma. Can you (SE) say.. well the remaining walls will take a bit of the sideways load and I''ll introduce a steel portal / box frame to take the rest and keep the steel sizes etc down or do I assume that the remaining walls don't make any contribution and design the steel frame to take all the load. Theoretically you can assume the former but a brick wall (and what is attaches to) behaves in a different way from the steel. Steel is more elastic than brick and it (steel) does not suddenly crack. An easy way of explaining this is to imagine that you connect together a plank of wood and the same size plank of steel with the strongest and stiffest glue you can imagine. Put your composite plank over a river and walk over it. (how you do that I don't know ) Both the steel and the wood will bend by the same amount as they are connected together. But steel is less elastic (stiffer) than the wood (called the modulus of elasticity, Youngs Modulus) so the steel will take more of the load than the wood as the wood is more "stretchy". This principle underpins the design of a flitch beam... it's very clever really but simple when you think about it. Suddenly the analysis becomes very complex and thus expensive design wise and even then the structural modelling of this is still only a model. Most SE's for practical purposes on small domestic applications (where the remaining walls are not enough) will design the steel to take all the vertical and sideways loads and limit the amount it moves by, so they don't crack the masonry excessively. This may seem like the SE's are being lazy.. but many know that while you could undertake a more refined analysis you will get tripped up when it comes to designing the connection between the steel and the masonry.. so back to square one. There is also the issue about how confident you are as to whether the builder will actually do what they are supposed to do. For small domestic stuff where supervision may be not as robust the simpler you make it the better, not just in terms of cost but also in terms of safety. To get the best value for this type of work you maybe want look at this in the round. Do you for example need to live in the house while work is going on, how hard / complex will it be to prop and so on. Will the size of the steel connections start to interfere with your window / thermal details ect. How much of a ceiling height can you live with vs downstand of a beam. I often find that the cost of the actual steel is not the main issue, it is the labour and complexity of the fixing of the steel to the existing building and the cost / labour involved in the temporary works. Sometimes you can skin the cat in another way where it's more economic to take the wall down above , take the load of the propping, put your steel in and rebuild the wall after... any takers?

A few words of encouragement. We have been designing rafts for many years (decades). The method is tried and tested, proven to work. Now we want to have rafts / basements with insulation (ICF) underneath.. the insulation is essentially just treated as another layer of soil... The structural engineering principles are the same, the harder part is the detail so you can avoid thermal bridging and so on, stop the building lifting up when the wind blows say. An old building may well have shallow founds and move about up and down between the seasons as the ground shrinks and swells. A ICF raft founded at the same depth as the original founds is more likely to move up and down at the same rate as the original house. It's common sense.. but you may need to spend a bit of money exposing the existing founds etc so the SE can justify the design. Find an SE that understands these principles and you are up and running.

Ta Raine for the heads up on what an Op is. Raine.. if you put in a bit of work here as it seems you are doing and start to make some contacts you could easily find yourself in a good spot, have money left over.. which will get spent on tv's, a nice hob, crapets, blinds, maybe some new pans if induction hob..etc. All the best with the project.

@DevilDamo Give me ten min while I figure out what an OP is, or can you or anyone help? Is an OP the same as on topic.. OT? Devil.. Do the planners fancy their chances faced with an evidenced based Arboriculturalists report covering say the health of the fauna backed up with an evidenced based foundation proposal from an SE in support. It's a bit like contractors getting into a spat when they don't actually have a leg to stand on. As a past contractor myself I have heard that this goes on (caveated etc for the faint of heart) So to answer the question... you have got to be a brave Planning Officer to refuse.. as if they do they could get full pelters while also being asked what the technical grounds for refusal are ..and the clock for them is ticking. For all BH members.. if you are willing to spend the time understanding the technical stuff and can present a recognised technical / evidenced based argument then the council have to consider this. "can the council still refuse to grant planning on the basis of the construction being within the RPA of the TPO?" @DevilDamoMy view is no, but the conditions attached may be so onerous that it is not practical to construct.

Hello Raine. I'm new to forums such as this. Have read around ebuild but was their demise due to the fact that they went commercial? You can sometimes make life easy here. Get your SE in early..if your serious then at some point you'll need the SE to design founds etc anyway. Get them working with Arboriculturalists. You'll probably find that with the right choice of folk they get on well. When you couple up the two you can end up with a pretty evidence based argument. In this case the " qualifications" are backed up with calculations and double PI cover? I worked on the SE design for the Tottenham Hotspur ground training ground gym a while back. Lots of TPO's .. RPA's (for all... to save you looking it up.. tree protection order, root protection area.. so you don't compact the soil round the roots and thus kill the tree anyway) the job was a joy as during the works we found the long jump pit that was used in the filming of Chariots of Fire. I spent a good while on gathering info for the desk top study, new about the film and so on (you get to spend time as an SE studying history and old interesting photos) , SI info etc. The planners / council were helpful to say the least.. good for the CPD and CV all round. Interestingly there were objections.. as not everyone supported spurs, and some folk just were just not that keen on footballers..and the "type they attacted" I can tell you that the deflection limits were reduced to accomodate the large mirrors on the walls. Part of the brief was that in order to train effectively you need to be able to see all of your body? In summary sometimes what initially seems to be a problem can be sorted with a different (people) approach.. don't always assume that the council / planners etc are going to be hostile from the outset. Often you get a communication that appears to be "official" ,and "hostile".. some folk are not that good at communicating and don't really mean to rub you up... after all you could be their Mum and Dad! Start off with the light touch, keep the big stick out of sight, hopefully you don't need to use it..

Good points Peter et al. You may wonder how he works this out! If you search the net for "guide to good lead work" then you will find extra advise and tips on what to do (laps etc) and what not. Make sure you read about patination oil as you don't want a nasty big lead oxcide (white) stain down the roof after you have done all the hard bit.

I'm a relative new comer to BH, but it seems that there are "no friends in the desert" on BH.. Rommel WW2.. maybe a take/adaptation on the French Legionnaires established circa 1831? Onoff still has time to finish the bathroom and the gate before BH birthday... last laugh and all that.